Bandwidth problems have long restricted the ability of cable television systems to provide private information services to subscribers. Such information services may include Internet access, video-on-demand, games, catalogs, etc. Private services may also include allowing the user to select from among hundreds of less popular programming that is thus made available only on a demand basis. One solution to the limits on system bandwidth has been to assign a portion of cable system bandwidth to conventional or popular channels that are universally broadcast to all subscribers. The remaining available channels are then available for assignment to requesting subscribers on a demand basis.
One such system for providing interactive services on a demand basis is described in U.S. Pat. No. 5,550,578. The full disclosure of this reference is hereby incorporated by reference herein. Basically the cable service distribution network divides the subscriber pool into various service areas, each served by a different trunk. A first group of channels broadcast to all service areas may provide conventional channels on channels 2 to 73 for example. A second group of channels, 74 to 79, for example, may be reserved for private information services. While the information on channels 2 to 73 is the same in each service area, the information on channels 74 to 79 is different in each service area. Of these channels, those that are in use are individually assigned to requesting subscribers. Subscribers receiving analog signals will use a full channel, those receiving digital signals will share the assigned channel with other subscribers on a packet addressed or time shared basis. A subscriber in one service area may be interacting on channel 74 at the same time a different subscriber in a different service area was also assigned to channel 74. The headend is equipped with the necessary processing, switching or splitting and combining systems for setting up these private channels on demand. Once assigned a channel for interactive services, the subscriber can request from any of a number of interactive services. Different interactive services may be accessed by the user requesting a different channel. For example, channels 80 to 300 can be virtual channels each of which accesses a different interactive service. As the subscriber continues to change channels among the interactive alternatives, the program being watched will change but the subscriber will remain tuned to the assigned channel for receiving interactive services. The information services can thus be provided to a subscriber over virtual channels in which the channel number changes for different interactive information services, even though the various information services may be provided over a fixed frequency input to the set top. The control data from the subscriber's set top can cause the back end to supply a different information service as the subscriber appears to be changing the channel.
Subscribers receive these interactive channels in a real time manner. If accessing a World Wide Web page in an interactive service a subscriber wishes to save the page, typically a video cassette recorder or printer attached to the set top would be required.